rules: Propagate PATH list from defaults

... instead of creating an ENV from it and propagating this.
The idea is to keep PATH entries separate and only join them
with ":" when we need it. In this way, we can accumulate
PATHs from multiple defaults later, and perform a
deduplication ("nub_left") to shorten the final string
length.

6 files changed, 225 insertions, 32 deletions

diff --git a/rules/CC/EXPRESSIONS b/rules/CC/EXPRESSIONS
index 2ebe7c17..cec5b8a2 100644
--- a/rules/CC/EXPRESSIONS
+++ b/rules/CC/EXPRESSIONS
@@ -90,6 +90,19 @@
     , "body": {"type": "CALL_EXPRESSION", "name": "map_provider"}
     }
   }
+, "default-PATH":
+  { "vars": ["defaults-transition"]
+  , "imports": {"list_provider": ["./", "..", "field_list_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "defaults"]
+      , ["provider", "PATH"]
+      , ["transition", {"type": "var", "name": "defaults-transition"}]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "list_provider"}
+    }
+  }
 , "default-TOOLCHAIN":
   { "vars": ["defaults-transition"]
   , "imports": {"map_provider": ["./", "..", "field_map_provider"]}
@@ -811,6 +824,7 @@
     , "objects": "objects"
     , "default-AR": "default-AR"
     , "default-ENV": "default-ENV"
+    , "default-PATH": "default-PATH"
     , "default-TOOLCHAIN": "default-TOOLCHAIN"
     , "default-NON_SYSTEM_TOOLS": "default-NON_SYSTEM_TOOLS"
     }
@@ -868,6 +882,36 @@
             ]
           }
         ]
+      , [ "ENV_PATH"
+        , { "type": "lookup"
+          , "map": {"type": "var", "name": "ENV"}
+          , "key": "PATH"
+          }
+        ]
+      , [ "ENV"
+        , { "type": "map_union"
+          , "$1":
+            [ {"type": "var", "name": "ENV"}
+            , { "type": "singleton_map"
+              , "key": "PATH"
+              , "value":
+                { "type": "join"
+                , "separator": ":"
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ {"type": "CALL_EXPRESSION", "name": "default-PATH"}
+                    , { "type": "if"
+                      , "cond": {"type": "var", "name": "ENV_PATH"}
+                      , "then": [{"type": "var", "name": "ENV_PATH"}]
+                      }
+                    ]
+                  }
+                }
+              }
+            ]
+          }
+        ]
       , ["objects", {"type": "CALL_EXPRESSION", "name": "objects"}]
       , [ "base name"
         , { "type": "if"
@@ -1079,6 +1123,7 @@
     , "flags": "flags"
     , "objects": "objects"
     , "default-ENV": "default-ENV"
+    , "default-PATH": "default-PATH"
     , "default-LDFLAGS": "default-LDFLAGS"
     , "default-TOOLCHAIN": "default-TOOLCHAIN"
     , "default-NON_SYSTEM_TOOLS": "default-NON_SYSTEM_TOOLS"
@@ -1115,6 +1160,36 @@
             ]
           }
         ]
+      , [ "ENV_PATH"
+        , { "type": "lookup"
+          , "map": {"type": "var", "name": "ENV"}
+          , "key": "PATH"
+          }
+        ]
+      , [ "ENV"
+        , { "type": "map_union"
+          , "$1":
+            [ {"type": "var", "name": "ENV"}
+            , { "type": "singleton_map"
+              , "key": "PATH"
+              , "value":
+                { "type": "join"
+                , "separator": ":"
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ {"type": "CALL_EXPRESSION", "name": "default-PATH"}
+                    , { "type": "if"
+                      , "cond": {"type": "var", "name": "ENV_PATH"}
+                      , "then": [{"type": "var", "name": "ENV_PATH"}]
+                      }
+                    ]
+                  }
+                }
+              }
+            ]
+          }
+        ]
       , ["hdrs", {"type": "empty_map"}]
       , ["objects", {"type": "CALL_EXPRESSION", "name": "objects"}]
       , [ "link-args"
diff --git a/rules/CC/RULES b/rules/CC/RULES
index 8af70beb..33b8520e 100644
--- a/rules/CC/RULES
+++ b/rules/CC/RULES
@@ -66,7 +66,7 @@
       ]
     , "PATH":
       [ "Path for looking up the compilers. Individual paths are joined"
-      , "with \":\"."
+      , "with \":\". Specifying this field extends values from \"base\"."
       ]
     }
   , "config_vars": ["ARCH", "HOST_ARCH"]
@@ -74,6 +74,7 @@
     { "base-provides": "defaults-base-provides"
     , "base-provides-list": "defaults-base-provides-list"
     , "artifacts_list": ["./", "..", "field_artifacts_list"]
+    , "nub_left": ["", "nub_left"]
     , "compile-deps": "compile-deps"
     , "compile-args-deps": "compile-args-deps"
     , "link-deps": "link-deps"
@@ -142,23 +143,26 @@
           , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
           }
         ]
-      , ["provider", "ENV"]
-      , ["default", {"type": "empty_map"}]
-      , [ "ENV"
-        , { "type": "if"
-          , "cond": {"type": "var", "name": "PATH"}
-          , "then":
-            { "type": "singleton_map"
-            , "key": "PATH"
-            , "value":
-              { "type": "join"
-              , "separator": ":"
-              , "$1": {"type": "var", "name": "PATH"}
+      , ["provider", "PATH"]
+      , [ "PATH"
+        , { "type": "++"
+          , "$1":
+            [ {"type": "var", "name": "PATH"}
+            , { "type": "++"
+              , "$1": {"type": "CALL_EXPRESSION", "name": "base-provides-list"}
               }
-            }
-          , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
+            ]
+          }
+        ]
+      , [ "PATH"
+        , { "type": "let*"
+          , "bindings": [["list", {"type": "var", "name": "PATH"}]]
+          , "body": {"type": "CALL_EXPRESSION", "name": "nub_left"}
           }
         ]
+      , ["provider", "ENV"]
+      , ["default", {"type": "empty_map"}]
+      , ["ENV", {"type": "CALL_EXPRESSION", "name": "base-provides"}]
       , ["provider", "NON_SYSTEM_TOOLS"]
       , ["default", {"type": "empty_map"}]
       , [ "NON_SYSTEM_TOOLS"
@@ -299,6 +303,7 @@
           , "CXXFLAGS"
           , "LDFLAGS"
           , "AR"
+          , "PATH"
           , "ENV"
           , "TOOLCHAIN"
           , "NON_SYSTEM_TOOLS"
diff --git a/rules/CC/auto/RULES b/rules/CC/auto/RULES
index 247ee016..0e156c98 100644
--- a/rules/CC/auto/RULES
+++ b/rules/CC/auto/RULES
@@ -156,6 +156,7 @@
     , "flags-cc": ["./", "..", "flags-cc"]
     , "flags-cxx": ["./", "..", "flags-cxx"]
     , "default-ENV": ["./", "..", "default-ENV"]
+    , "default-PATH": ["./", "..", "default-PATH"]
     , "default-TOOLCHAIN": ["./", "..", "default-TOOLCHAIN"]
     , "default-NON_SYSTEM_TOOLS": ["./", "..", "default-NON_SYSTEM_TOOLS"]
     }
@@ -222,6 +223,36 @@
             ]
           }
         ]
+      , [ "ENV_PATH"
+        , { "type": "lookup"
+          , "map": {"type": "var", "name": "ENV"}
+          , "key": "PATH"
+          }
+        ]
+      , [ "ENV"
+        , { "type": "map_union"
+          , "$1":
+            [ {"type": "var", "name": "ENV"}
+            , { "type": "singleton_map"
+              , "key": "PATH"
+              , "value":
+                { "type": "join"
+                , "separator": ":"
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ {"type": "CALL_EXPRESSION", "name": "default-PATH"}
+                    , { "type": "if"
+                      , "cond": {"type": "var", "name": "ENV_PATH"}
+                      , "then": [{"type": "var", "name": "ENV_PATH"}]
+                      }
+                    ]
+                  }
+                }
+              }
+            ]
+          }
+        ]
       , [ "c.flags"
         , { "type": "BLOB"
           , "data":
diff --git a/rules/CC/pkgconfig/EXPRESSIONS b/rules/CC/pkgconfig/EXPRESSIONS
index 4c174c40..535faf6b 100644
--- a/rules/CC/pkgconfig/EXPRESSIONS
+++ b/rules/CC/pkgconfig/EXPRESSIONS
@@ -1,6 +1,9 @@
 { "pkgconfig result":
   { "vars": ["ENV", "name", "args", "stage"]
-  , "imports": {"default-ENV": ["./", "..", "default-ENV"]}
+  , "imports":
+    { "default-ENV": ["./", "..", "default-ENV"]
+    , "default-PATH": ["./", "..", "default-PATH"]
+    }
   , "expression":
     { "type": "let*"
     , "bindings":
@@ -12,6 +15,36 @@
             ]
           }
         ]
+      , [ "ENV_PATH"
+        , { "type": "lookup"
+          , "map": {"type": "var", "name": "ENV"}
+          , "key": "PATH"
+          }
+        ]
+      , [ "ENV"
+        , { "type": "map_union"
+          , "$1":
+            [ {"type": "var", "name": "ENV"}
+            , { "type": "singleton_map"
+              , "key": "PATH"
+              , "value":
+                { "type": "join"
+                , "separator": ":"
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ {"type": "CALL_EXPRESSION", "name": "default-PATH"}
+                    , { "type": "if"
+                      , "cond": {"type": "var", "name": "ENV_PATH"}
+                      , "then": [{"type": "var", "name": "ENV_PATH"}]
+                      }
+                    ]
+                  }
+                }
+              }
+            ]
+          }
+        ]
       , [ "cflags-filename"
         , {"type": "join", "$1": [{"type": "var", "name": "name"}, ".cflags"]}
         ]
diff --git a/rules/CC/proto/EXPRESSIONS b/rules/CC/proto/EXPRESSIONS
index 84d3d55e..29c205c2 100644
--- a/rules/CC/proto/EXPRESSIONS
+++ b/rules/CC/proto/EXPRESSIONS
@@ -51,6 +51,19 @@
     , "body": {"type": "CALL_EXPRESSION", "name": "map_provider"}
     }
   }
+, "default-PATH":
+  { "vars": ["defaults-transition"]
+  , "imports": {"list_provider": ["./", "../..", "field_list_provider"]}
+  , "expression":
+    { "type": "let*"
+    , "bindings":
+      [ ["fieldname", "proto-defaults"]
+      , ["provider", "PATH"]
+      , ["transition", {"type": "var", "name": "defaults-transition"}]
+      ]
+    , "body": {"type": "CALL_EXPRESSION", "name": "list_provider"}
+    }
+  }
 , "default-TOOLCHAIN":
   { "vars": ["defaults-transition"]
   , "imports": {"map_provider": ["./", "../..", "field_map_provider"]}
@@ -118,6 +131,7 @@
     , "default-LDFLAGS": "default-LDFLAGS"
     , "default-GRPC_PLUGIN": "default-GRPC_PLUGIN"
     , "default-ENV": "default-ENV"
+    , "default-PATH": "default-PATH"
     , "default-TOOLCHAIN": "default-TOOLCHAIN"
     , "default-NON_SYSTEM_TOOLS": "default-NON_SYSTEM_TOOLS"
     }
@@ -172,7 +186,7 @@
             }
           }
         ]
-      , [ "protoc-ENV"
+      , [ "ENV"
         , { "type": "map_union"
           , "$1":
             [ {"type": "CALL_EXPRESSION", "name": "default-ENV"}
@@ -180,6 +194,36 @@
             ]
           }
         ]
+      , [ "ENV_PATH"
+        , { "type": "lookup"
+          , "map": {"type": "var", "name": "ENV"}
+          , "key": "PATH"
+          }
+        ]
+      , [ "protoc-ENV"
+        , { "type": "map_union"
+          , "$1":
+            [ {"type": "var", "name": "ENV"}
+            , { "type": "singleton_map"
+              , "key": "PATH"
+              , "value":
+                { "type": "join"
+                , "separator": ":"
+                , "$1":
+                  { "type": "++"
+                  , "$1":
+                    [ {"type": "CALL_EXPRESSION", "name": "default-PATH"}
+                    , { "type": "if"
+                      , "cond": {"type": "var", "name": "ENV_PATH"}
+                      , "then": [{"type": "var", "name": "ENV_PATH"}]
+                      }
+                    ]
+                  }
+                }
+              }
+            ]
+          }
+        ]
       , ["protoc-deps", {"type": "CALL_EXPRESSION", "name": "protoc-deps"}]
       , [ "proto srcs"
         , { "type": "disjoint_map_union"
diff --git a/rules/CC/proto/RULES b/rules/CC/proto/RULES
index cfc3786e..4ffc73b2 100644
--- a/rules/CC/proto/RULES
+++ b/rules/CC/proto/RULES
@@ -51,13 +51,14 @@
       ]
     , "PATH":
       [ "Path for looking up the proto compiler. Individual paths are joined"
-      , "with \":\"."
+      , "with \":\". Specifying this field extends values from \"base\"."
       ]
     }
   , "imports":
     { "base-provides": ["./", "..", "defaults-base-provides"]
     , "base-provides-list": ["./", "..", "defaults-base-provides-list"]
     , "artifacts_list": ["", "field_artifacts_list"]
+    , "nub_left": ["", "nub_left"]
     , "compile-deps": ["CC", "compile-deps"]
     , "compile-args-deps": ["CC", "compile-args-deps"]
     , "link-deps": ["CC", "link-deps"]
@@ -99,23 +100,26 @@
           , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
           }
         ]
-      , ["provider", "ENV"]
-      , ["default", {"type": "empty_map"}]
-      , [ "ENV"
-        , { "type": "if"
-          , "cond": {"type": "var", "name": "PATH"}
-          , "then":
-            { "type": "singleton_map"
-            , "key": "PATH"
-            , "value":
-              { "type": "join"
-              , "separator": ":"
-              , "$1": {"type": "var", "name": "PATH"}
+      , ["provider", "PATH"]
+      , [ "PATH"
+        , { "type": "++"
+          , "$1":
+            [ {"type": "var", "name": "PATH"}
+            , { "type": "++"
+              , "$1": {"type": "CALL_EXPRESSION", "name": "base-provides-list"}
               }
-            }
-          , "else": {"type": "CALL_EXPRESSION", "name": "base-provides"}
+            ]
+          }
+        ]
+      , [ "PATH"
+        , { "type": "let*"
+          , "bindings": [["list", {"type": "var", "name": "PATH"}]]
+          , "body": {"type": "CALL_EXPRESSION", "name": "nub_left"}
           }
         ]
+      , ["provider", "ENV"]
+      , ["default", {"type": "empty_map"}]
+      , ["ENV", {"type": "CALL_EXPRESSION", "name": "base-provides"}]
       , ["provider", "NON_SYSTEM_TOOLS"]
       , ["default", {"type": "empty_map"}]
       , [ "NON_SYSTEM_TOOLS"
@@ -214,6 +218,7 @@
           [ "PROTOC"
           , "LDFLAGS"
           , "GRPC_PLUGIN"
+          , "PATH"
           , "ENV"
           , "TOOLCHAIN"
           , "NON_SYSTEM_TOOLS"